Pseudocerastes urarachnoides is a fascinating viper and as yet has been reported only in western Iran. An elaborated arachnid-like caudal structure is a unique feature of this viper, hence gives it the common name “Iranian spider-tailed viper”. During tail wagging, the structure is reminiscent of a moving spider. Tail movements are used for two different purposes in snakes: defense via tail vibration and hunting via both caudal luring and caudal distraction. Caudal luring in snakes is the wriggling or wagging of the posterior part of tail, in the presence of a potential prey, with conspicuous color pattern while the rest of body is cryptically colored. Previous studies have speculated on the role of caudal structure of P. urarachnoides in hunting. Our 2.5-year study has revealed that development of the structure of the caudal lure is commenced after birth and is linearly correlated to snout-vent length. The caudal lure attracts some species of birds. Caudal luring behavior is carried out both in the presence and absence of birds. The findings are reported for the first time and confirmed by direct observation of undisturbed individuals in the field.

RabatskyA.M. (2008):
Caudal luring as a precursor in the evolution of the rattle: a test using an ancestral rattlesnake, Sistrurus miliarius barbouri. In:
The Biology of Rattlesnakes p.
143-154.
HayesW.K.BeamanK.R.CardwellM.D.BushS.P. Eds Loma Linda University PressLoma Linda, CA.

A diagram showing the frequency of tail luring in Pseudocerastes urarachnoides in the absence and presence of avian prey. Those five peaks with frequencies higher than 0.3 and black solid asterisks above, indicating caudal luring when avian preys present. This figure is published in colour in the online version.

A complete scene of predation on birds by the Iranian spider-tailed viper, Pseudocerastes urarachnoides. (a) A motionless Iranian spider-tailed viper while caudal luring, (b) attacking the tail by bird, (c-d) fleeing from the vipers fang, (e) returning toward the caudal lure, (f) pecking the tail, (g) striking of this viper, (h) biting and envenoming the prey on the head, (i) fluttering for escape, (j) simultaneously swallowing and pulling in the dead bird. This figure is published in colour in the online version.

A diagram showing the frequency of tail luring in Pseudocerastes urarachnoides in the absence and presence of avian prey. Those five peaks with frequencies higher than 0.3 and black solid asterisks above, indicating caudal luring when avian preys present. This figure is published in colour in the online version.

A complete scene of predation on birds by the Iranian spider-tailed viper, Pseudocerastes urarachnoides. (a) A motionless Iranian spider-tailed viper while caudal luring, (b) attacking the tail by bird, (c-d) fleeing from the vipers fang, (e) returning toward the caudal lure, (f) pecking the tail, (g) striking of this viper, (h) biting and envenoming the prey on the head, (i) fluttering for escape, (j) simultaneously swallowing and pulling in the dead bird. This figure is published in colour in the online version.